Oxidative stress, resulting from excess generation of reactive oxygen species (ROS) by mitochondria, is believed to contribute to the process of aging. Whether in vivo or in vitro, animal tissues exhibit a certain profile of metabolites, determined conjointly by the metabolic rate of the tissue, the accumulation of oxidative end products (biomarkers), and the levels of cellular antioxidative defense mechanisms. The metabolic profile and biomarkers represent the "fingerprints" of a tissue and may reflect both inherent longevity and exposure to oxidative stress. It was recently shown that overexpression of human superoxide dismutase (SOD1) in Drosophila melanogaster motor neurons could greatly extend its life span. This suggests that neuronal resistance to oxidative stress can directly translate to the extension of life span in fruit flies. The relationship between life span and neuronal resistance to oxidative stress in mammals, however, has not been studied. It also remains to be determined whether neural tissues from a longerlived animal generate less ROS and thus remain healthier than controls. The longevity of rats can be extended as a result of calorie restriction. There is also reason to believe that life span can be altered epigenetically by diet manipulation (e.g., in the epigenetic mouse model), a focus of Project 4. In this project, we will test the hypothesis that diet-induced life extension involves reduced neuronal damage from oxidative stress either through decreased metabolic generation of free radicals or augmented protective mechanisms. The Specific Aims of this project are: (1) Determine whether the nervous system of a longer-lived animal enhances antioxidant defenses or generates less ROS than a control animal. (2) Determine in vivo whether the central nervous system (represented by retina as an experimentally accessible compartment) of a longer-lived animal is more resistant to oxidative stress than that of a control animal. (3) Determine whether neurons cultured in vitro from a longer-lived animal are intrinsically more resistant to oxidative stress or less prone to generate ROS than those from a control animal. Data obtained from these experiments should reveal whether neurons from these longer-lived animals generate less ROS and result in less cell damage than those of control animals. Furthermore, we will determine whether the nervous systems in longer-lived animals can manage challenges better when given an external insult of oxidative stress.